KCSAN: data-race in do_exit / futex_wait_queue

KCSAN: data-race in do_exit / futex_wait_queue_me (3)
Status: auto-closed as invalid on 2021/02/08 21:09
Reported-by: syzbot+5d5fd1007b1fd0a5fa9b@syzkaller.appspotmail.com
First crash: 255d, last: 202d

similar bugs (3):
Kernel	Title	Count	Last	Reported	Patched	Status
upstream	KCSAN: data-race in do_exit / futex_wait_queue_me (2)	1	300d	300d	0/22	auto-closed as invalid on 2020/11/02 08:53
upstream	KCSAN: data-race in do_exit / futex_wait_queue_me (4)	5	71d	127d	0/22	auto-closed as invalid on 2021/06/19 09:40
upstream	KCSAN: data-race in do_exit / futex_wait_queue_me	3	361d	391d	0/22	auto-closed as invalid on 2020/09/02 20:47

Sample crash report:

==================================================================
BUG: KCSAN: data-race in do_exit / futex_wait_queue_me

read-write to 0xffff88810c80b02c of 4 bytes by task 30478 on cpu 0:
 freezer_count include/linux/freezer.h:121 [inline]
 freezable_schedule include/linux/freezer.h:173 [inline]
 futex_wait_queue_me+0x198/0x240 kernel/futex.c:2602
 futex_wait+0x145/0x3d0 kernel/futex.c:2704
 do_futex+0x105a/0x20c0 kernel/futex.c:3763
 __do_sys_futex kernel/futex.c:3826 [inline]
 __se_sys_futex+0x2a8/0x390 kernel/futex.c:3792
 __x64_sys_futex+0x74/0x80 kernel/futex.c:3792
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88810c80b02c of 4 bytes by task 30480 on cpu 1:
 find_alive_thread kernel/exit.c:511 [inline]
 find_new_reaper kernel/exit.c:560 [inline]
 forget_original_parent kernel/exit.c:635 [inline]
 exit_notify kernel/exit.c:668 [inline]
 do_exit+0x59c/0x1690 kernel/exit.c:845
 do_group_exit+0x16f/0x170 kernel/exit.c:922
 __do_sys_exit_group+0xb/0x10 kernel/exit.c:933
 __se_sys_exit_group+0x5/0x10 kernel/exit.c:931
 __x64_sys_exit_group+0x16/0x20 kernel/exit.c:931
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 30480 Comm: syz-executor.5 Not tainted 5.11.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================

Crashes (3):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	VM info
ci2-upstream-kcsan-gce	2021/01/04 21:08	upstream	36bbbd0e234d	2a28ff1f	.config	log	report	info
ci2-upstream-kcsan-gce	2020/12/14 20:20	upstream	2c85ebc57b3e	97183ed7	.config	log	report	info
ci2-upstream-kcsan-gce	2020/11/12 00:41	upstream	3d5e28bff7ad	cca87986	.config	log	report	info